The invention relates to polyurethane solutions with alkoxysilane structural units, processes for the preparation of polyurethane solutions containing alkoxysilane structural units and the use of polyurethane solutions containing alkoxysilane structural units.
Polyurethane solutions have been known for a long time, e.g. D. Diederich, Methoden der Organischen Chemie [Methods of Organic Chemistry] (Houben-Weyl), volume, E 20, Georg Thieme Verlag, 1997 and the literature cited there.
As a rule, polyurethane solutions are high molecular weight reaction products of aliphatic and/or aromatic di- or polyisocyanates with di- or trifunctional polyols and/or diamines. The reaction of the isocyanate-functional compounds with the hydroxyl- and/or amino-functional compounds takes place here close to the equivalence point to achieve the desired high molecular weights.
To obtain products which are soluble and readily processable, the chain build-up reaction must be stopped when the desired molecular weights or viscosities of the polyurethane solutions are reached. This is usually effected by addition of low molecular weight reactive compounds, such as e.g. monoamine (DE-A 2 633 293), monoisocyanate or acetic anhydride (DE-A 2 500 921, EP-A 129 396), by addition of reactive monofunctional alcohols, such as methanol, or by addition of other compounds having a chain-stopping action, such as e.g. butanone oxime (DE-A 3 142 706).
In technical practice, as a rule a certain excess of stopper reagent is added here in order to ensure reliable stopping. However, this excess can have an adverse effect on coating properties, which can manifest itself e.g. by an odour nuisance, by exudation, by adhesion problems and by the formation of defects in the film due to bubbles and cratering. The storage stability of such solutions can also be impaired as a result. Excess free monoamine, monoisocyanate or even excess reactive monoalcohol can lead to considerable changes in viscosity up to serious degradation phenomena, associated with a loss in properties, due to a creeping reaction with urethane or ester bonds in the polymer, especially during the storage times which are unavoidable in practice.
Since polyurethane solutions as a rule no longer contain reactive end groups, only physical drying takes place after application. Chemical crosslinking via reactive groups at the chain end to form very high molecular weight polymers with an improved level of properties is thus no longer possible.
DE-A 3 401 753 discloses polyurethane solutions with terminal aromatic amino groups which are available for a later crosslinking reaction. However, this requires subsequent addition of a reaction partner.
JP 0 8253 545 describes crosslinkable urethane resin compositions which comprise compounds with two isocyanate-reactive groups and a hydrolysable silyl group. The urethane resins comprise exclusively laterally bonded silyl groups. This leads to crosslinked adhesives or coatings with a high hardness, but only a low elasticity or extensibility. Compounds with two isocyanate-reactive groups and a hydrolysable groups are furthermore unsuitable as a stopper reagent.
The object of the invention was therefore to provide polyurethane solutions which do not have the disadvantages mentioned. In particular, polyurethane solutions which comprise polyurethanes with high molecular weights, can be prepared and stopped reliably, and furthermore when used in coatings cause no problems due to odour nuisance, exudation, inadequate adhesion or inadequate optical properties of the film are to be provided. It must be ensured here that any excess amounts of stopper agent added do not have an adverse effect on the storage stability of the solution and on the properties of the coating, and also that no harmful effect on the health of processors and workers is to be expected.
Surprisingly, it has now been found that polyurethane solutions which comprise in incorporated form compounds with an isocyanate-reactive group and at least one alkoxysilane group as a stopper agent meet the stated requirements. Moreover, an improved stability to hydrolysis, a very good adhesion and a particularly pleasant handle of coatings based on the polyurethane solutions according to the invention have also surprisingly been found. Surprisingly, it has also been found that the polyurethane solutions according to the invention are very particularly suitable for the production of high-quality coatings with a high permeability to water vapour and, associated with this, an excellent wearing comfort. The coatings according to the invention combine here a high permeability to water vapour with a very good water resistance or wet-fastness and a relatively low swelling in water.
Polyurethane solutions which comprise in incorporated form a compound with an isocyanate-reactive group and an alkoxysilane group as a stopper agent and additionally a compound with at least two isocyanate-reactive groups and at least one alkoxysilane structural unit in small amounts surprisingly likewise lead to coatings which meet the abovementioned requirements and moreover have both excellent mechanical properties of the films, in particular a high extensibility and elasticity, and at the same time very high melting or softening temperatures, which is very advantageous for many applications, e.g. in coating of textiles.
Polyurethane solutions which comprise as the stopper agent a reaction product, containing aspartic acid ester structural units, of a compound with a primary amino group and at least one alkoxysilane group with a maleic acid dialkyl ester surprisingly also meet the abovementioned requirements, in spite of the known reduced reactivity of the aspartic acid ester structural units. They moreover have the further advantage that larger amounts of stopper agent are also employed, also at a very early point in time of the reaction and also without the presence of organic solvents, without the risk of the formation of sparingly soluble or insoluble ureas of gel particles. Furthermore, on the other hand coatings which have, in addition to excellent mechanical properties of the film, an excellent, particularly soft handle and a very high wearing comfort, which is very important for many uses, surprisingly can be obtained.
The invention therefore provides polyurethane solutions with alkoxysilane structural units, characterized in that they are reactions products, in organic solution, of
a) at least one at least difunctional polyol of molecular weight 500 to 16,000,
b) at least one at least difunctional polyisocyanate of molecular weight 140 to 1,500,
c) at least one low molecular weight at least difunctional alcohol and/or amine of molecular weight 32 to 500,
d) at least one compound containing at least one alkoxysilane group and an isocyanate-reactive group and
e) optionally a monofunctional substance with an amino, alcohol or oxime group,
the amount of stopper agent equivalents from component d) being at least 50% of the total amount of stopper agent from d) and e).
The invention preferably provides polyurethane solutions with alkoxysilane structural units, characterized in that they are reaction products, in organic solution, of
a) 40 to 92 wt. % of at least one at least difunctional polyol of molecular weight 500 to 16,000,
b) 7 to 50 wt. % of at least one at least difunctional polyisocyanate of molecular weight 140 to 1,500,
c) 0.5 to 20 wt. % of at least one low molecular weight at least difunctional alcohol and/or amine of molecular weight 32 to 500,
d) 0.1 to 5 wt. % of at least one compound containing at least one alkoxysilane group and an isocyanate-reactive group and
e) optionally a monofunctional substance with an amino, alcohol or oxime group,
the amount of stopper agent equivalents from component d) being at least 75% of the total amount of stopper agent from d) and e).
The invention particularly preferably provides polyurethane solutions, characterized in that they are reaction products, in organic solution, of
a) 47 to 88 wt. % of at least one at least difunctional polyol of molecular weight 500 to 16,000,
b) 10 to 40 wt. % of at least one at least difunctional polyisocyanate of molecular weight 140 to 1,500,
c) 0.8 to 17 wt. % of at least one low molecular weight at least difunctional alcohol and/or amine of molecular weight 32 to 500,
d) 0.2 to 3.0 wt. % of at least one compound containing an alkoxysilane group and an isocyanate-reactive group and
e) 0-0.5 wt. % of a monofunctional substance with an amino, alcohol or oxime group, the amount of stopper agent equivalents from component d) being at least 95% of the total amount of stopper agent from d) and e).
The invention also provides a process for the preparation of polyurethane solutions with alkoxysilane structural units, characterized in that an isocyanate-functional polyurethane is first prepared in a one- or two-stage reaction from at least one polyol a) and at least one difunctional polyisocyanate b), optionally co-using a low molecular weight component c), and then optionally undergoes a further build up in molecular weight in a further reaction step by reaction with an at least difunctional component c), and is reacted in a concluding reaction step with at least one compound d) containing an alkoxysilane group and an isocyanate-reactive group, optionally co-using a monofunctional component e), to give a high molecular weight polyurethane with alkoxysilane structural units which no longer contains free isocyanate groups, an organic solvent being added either before, during or after the first reaction step in an amount such that the resulting polyurethane solution with alkoxysilane end groups has a solids content of 9 to 65 wt. %.
The invention also provides the use of polyurethane solutions containing alkoxysilane structural units in paints, coatings, sealants and/or adhesives.
The term polyurethane solution also includes polyurethane-polyurea solutions, and also solutions which comprise e.g. trimer, uretdione, allophanate and/or biuret structural units in minor amounts, in addition to urethane and/or urea structural units. As a rule, the solutions are clear, but solutions which have a cloudy or opaque appearance are also included, although this is less preferred.
Polyol components a) which are suitable for the preparation of the polyurethane solutions according to the invention are e.g. polyester polyols (e.g. Ullmanns Enzyklopxc3xa4die der technischen Chemie [Ullmanns Encyclopaedia of Industrial Chemistry], 4th edition, volume 19, p. 62-65). Suitable raw materials for the preparation of these polyester polyols are difunctional alcohols, such as ethylene glycol, 1,2- and 1,3-propylene glycol, 1,3-, 1,4- and 2,3-butanediol, 1,6-hexanediol, neopentylglycol, trimethylhexanediol, triethylene glycol, tetraethylene glycol, hydrogenated bisphenols, trimethylpentanediol, diethylene diglycol, dipropylene diglycol, 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol and difunctional carboxylic acids or anhydrides thereof, such as adipic acid, phthalic acid (anhydride), isophthalic acid, maleic acid (anhydride), terephthalic acid, tetrahydrophthalic acid (anhydride), hexahydrophthalic acid (anhydride), succinic acid (anhydride), fumaric acid, azelaic acid and dimer fatty acids. Polyester raw materials which are also suitable for co-use in minor amounts are monocarboxylic acids, such as benzoic acid, 2-ethylhexanoic acid, oleic acid, soya oil fatty acid, stearin fatty acid, groundnut oil fatty acid, linseed oil fatty acid, nonanoic acid, cyclohexanemonocarboxylic acid, isononanoic acid, sorbic acid and conjuene fatty acid, carboxylic acids or alcohols of higher functionality, such as trimellitic acid (anhydride), butanetetracarboxylic acid, trimer fatty acids, trimethylolpropane, glycerol, pentaerythritol, castor oil and dipentaerythritol, and other polyester raw materials not mentioned by name.
Polyol components a) which are also suitable are polycarbonate diols which can be obtained e.g. by reaction of diphenyl carbonate or dimethyl carbonate with low molecular weight di- or triols or epsilon-caprolactone-modified di- or triols.
Polyol components a) which are also suitable are hydroxy-functional silicones or polysiloxanes, such as e.g. Baysilon(trademark) OF (Bayer A G).
Lactone-based polyester diols are also suitable, these being homo- or copolymers of lactones, preferably addition products, containing terminal hydroxyl groups, of lactones, such as e.g. epsilon-caprolactone or gamma-butyrolactone, on difunctional starter molecules. Suitable starter molecules can be the abovementioned diols, or also low molecular weight polyester diols or polyether diols. Instead of the polymers of lactones, the corresponding hdyroxycarboxylic acids can also be employed.
Polyol components a) which are also suitable are polyether polyols. They are obtainable e.g. by polymerization of ethylene oxide, propylene oxide and/or tetrahydrofuran by themselves, e.g. in the presence of BF3 or basic catalysts, or by addition of these compounds, optionally also as a mixture or in succession, on to starter components with reactive hydrogen atoms, such as alcohols, amines, amino-alcohols or water.
The polyol components a) mentioned can also be employed as mixtures, optionally also together with other polyols a), such as e.g. polyester amides, polyether esters, polyacrylates or polyols based on epoxy resins.
The hydroxyl number of the polyols a) is 5 to 350, preferably 8 to 200 mg KOH/g substance. The molecular weights of the polyols a) are between 500 and 25,000, preferably between 500 and 15,000, at least a portion of polyols a) with a molecular weight of  greater than 9,000 g/mol being employed in a preferred embodiment.
Preferred components a) are hydrolysis-stable polyols of molecular weight 300 to 3,500, in particular 900 to 2,500, in particular comprising to the extent of at least 50% polycarbonate diols, which can be employed together with tetrahydrofuran diols and/or di- or trifunctional polyethers based on propylene oxide or propylene oxide/ethylene oxide, or mixtures of the hydrolysis-stable polyols mentioned, where, if trifunctional polyether polyols are used, these are employed at most in amounts of up to 4 wt. %, based on the total solids content of the polymer. These hydrolysis-stable polyols can also be employed together with polyester polyols, preferably polyester polyols with a comparatively good stability to hydrolysis, such as e.g. polyesters based on phthalic anhydride, isophthalic acid, dimer fatty acid, hexanediol and/or neopentylglycol.
In another preferred embodiment, hydrophilic polyols, such as e.g. ethylene oxide polyethers, ethylene oxide/propylene oxide polyethers or polyesters based on triethylene glycol or tetraethylene glycol and dicarboxylic acids, are employed as component a) in amounts such that coatings prepared with them are permeable to water vapour. The polyurethane then preferably comprises as component a) 10 to 60 wt. % hydrophilic polyols, in addition to 23 to 50 wt. % non-hydrophilic polyols, in each case based on the total solids content of the polyurethane, the total amount of component a) being not more than 92 wt. % of the total solids content of the polyurethane.
Corresponding polyurethane solutions are very particularly suitable for the preparation of high-quality coatings with a high permeability to water vapour and the excellent wearing comfort associated therewith. The coatings according to the invention combine here a high permeability to water vapour with a very good water resistance or wet-fastness and a relatively low swelling in water.
The total content of hydrophilic constituentsxe2x80x94polyols a) and optionally hydrophilic diols or diamines d)xe2x80x94here is 10 to 60, preferably 20 to 45 wt. %, based on the total solids content of the polyurethane solution.
Component b) comprises at least one organic at least difunctional polyisocyanate of molecular weight 140 to 1,500, preferably 168 to 500. Suitable polyisocyanates are e.g. hexamethylene-diisocyanate (HDI), isophorone-diisocyanate (IPDI), 4,4xe2x80x2-diisocyanato-dicyclohexylmethane (HI2MDI), 1,4-butane-diisocyanate, H6-2,4- and/or -2,6-diisocyanato-toluene, hexahydrodiisocyanatoxylene, 2,4- or 2,6-diisocyanatotoluene (TDI), xylylene-diisocyanate and 4,4xe2x80x2-diisocyanatodiphenylmethane (MDI). Polyisocyanates which are known per se and are based on the isocyanates mentioned and also other isocyanates and have uretdione, biuret, isocyanurate, iminoxadiazinedione or urethane structural units can also be co-used, but this is not preferred.
The exclusive use of aliphatic and/or cycloaliphatic difunctional isocyanates of molecular weight 168 to 262, such as isophorone-diisocyanate and/or hexamethylene-diisocyanate and/or diisocyanatodicyclohexylmethane (Desmodur(trademark) W, Bayer A G) and/or H6-2,4- and/or -2,6-diisocyanatotoluene, is preferred, component b) particularly preferably comprising isophorone-diisocyanate or H6-2,4- and/or -2,6-diisocyanatotoluene to the extent of at least 75 wt. %.
The exclusive use of aromatic diisocyanates of molecular weight 174 to 280, in particular 2,4- and/or 2,6-diisocyanatotoluene and/or 4,4xe2x80x2-diisocyanatodiphenylmethane, is also preferred.
In a preferred embodiment, difunctional isocyanates containing allophanate groups are employed as component b). Such components are obtained by reacting a diisocyanate, preferably aromatic diisocyanates, such as e.g. MDI or TDI, with aliphatic linear monoalcohols having 4 to 18 carbon atoms, such as e.g. n-butanol, hexanol, 2-ethylhexanol or stearyl alcohol, optionally using suitable catalysts, such as e.g. zinc acetylacetonate, at temperatures of e.g. 40 to 110xc2x0 C. to form allophanate. The reaction here of 2 molecules of diisocyanate with one molecule of monoalcohol leads to the formation of a diisocyanate with an allophanate structural unit, it also being possible for higher homologues to be formed. It is also possible to carry out the allophanate formation in situ during the build-up of the polyurethane according to the invention. Surprisingly, the co-use of diisocyanates containing allophanate groups leads to polyurethanes which allow the production of coatings with particularly good resistance properties, e.g. to the action of solvents or to water, and a pleasant handle.
Component c) is at least one low molecular weight compound of the molecular weight range of 32 to 500 with at least two groups which are reactive towards isocyanate groups. These reactive groups are preferably hydroxyl and/or primary or secondary amino groups.
Suitable components c) are e.g. ethylene glycol, 1,2- or 1,3-propylene glycol, 1,4-butanediol, neopentylglycol, 1,6-hexanediol, trimethylpentanediol, trimethylolpropane, glycerol, the reaction product of 2 mol propylene carbonate and 1 mol hydrazine, ethylenediamine, diethylenetriamine, isophoronediamine, hexamethylenediamine, acetone-azine, 4,4-diaminodicyclohexylmethane, hydroxyethylethylenediamine, ethanolamine, diethanolamine, isopropanolamine, diisopropanolamine, N-methylethanolamine, aminomethylpropanol, hydrazine (hydrate), propylenediamine, dimethylethylenediamine, adipic acid dihydrazide, 2-aminoethyl aminoethanesulfonate, the 1:1 reaction product of acrylic acid and isophoronediamine or ethylenediamine, dimethylolacetic acid, 2,2xe2x80x2-dimethylolpropionic acid, 2,2xe2x80x2-dimethylolbutyric acid, 2,2xe2x80x2-dimethylolpentanoic acid, sulfonate diols optionally containing ether groups, of the type described in U.S. Pat. No. 4,108,814, amino-functional sulfonates with one or two amino groups and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane.
If a component c) is co-used in the first reaction step carried out in one stage or two stages, dihydroxy-functional compounds are preferably employed, in particular ethylene glycol, 1,4-butanediol, 1,6-hexanediol or sulfonate diols containing ether groups.
If a component c) is employed in the second reaction step, preferably after addition of solvent, diamino-functional compounds are preferably employed, in particular ethylenediamine, isophoronediamine, 4,4-diaminodicyclohexylmethane, hydrazine (hydrate), adipic acid dihydrazide or 2-aminoethyl aminoethanesulfonate.
In a preferred embodiment, diamino-functional components c) containing alkoxysilane groups are co-used as chain-lengthening agents, preferably in amounts of up to 2 wt. %. The use of larger amounts of such components c) surprisingly leads to polyurethane solutions which, when used as coatings, result in a too high a hardness, too low an extensibility or elasticity, above all at low temperatures, and a relatively hard, cold and rather unpleasant handle.
In a preferred embodiment, hydrophilic difunctional components of the abovementioned type containing salt groups are employed as component c) in amounts of 2 to 16 wt. %, particularly preferably 2.5 to 13 wt. %, optionally in combination with hydrophilic polyols a), in order to impart to the corresponding coatings a character which is permeable to water vapour.
Hydrophilic components c) are particularly preferably employed here together with the abovementioned hydrophilic polyols a). Coatings with a particularly high permeability to water vapour can be produced as a result.
In a preferred embodiment, hydrazine (hydrate), adipic acid dihydrazide and/or the reaction product of 2 mol propylene carbonate and 1 mol hydrazine are co-used as component c) in amounts of 0.1 to 4.5 wt. %. Polyurethane solutions with a particularly high stability towards heat and discoloration can be obtained here.
Alkoxysilanes which are suitable as component d) are aminoalkylsiloxanes, such as e.g. 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltributoxysilane, 2-aminoethyltriethoxysilane, 2-aminoethyltrimethoxysilane, 2-aminoethyltributoxysilane, 4-aminobutyltriethoxysilane, 4-aminobutyltrimethoxysilane, reaction products of the alkoxysilanes mentioned with maleic acid dialkyl esters, such as e.g. maleic acid diethyl ester, maleic acid dimethyl ester or maleic acid dibutyl ester, N-phenylaminopropyltrimethoxysilane, bis-(3-trimethoxysilylpropyl)amine, compounds of the type mentioned in which one or two of the alkoxy groups are replaced by alkyl groups and mixtures of the alkoxysilanes mentioned and also other alkoxysilanes.
Components d) are employed in amounts of 0.1 to 5, preferably 0.2 to 3.0, particularly preferably 0.3 to 1.3 wt. %.
In a preferred embodiment, the mathematically determined content of xe2x80x94Sixe2x80x94(Oxe2x80x94)3 structural units of the solids of the polyurethane solutions is less than 1.2 wt. %. With these e.g. coatings for textiles and leather with a high level of mechanical properties, in particular regarding extensibility and elasticity, and a pleasantly soft handle can be obtained. Higher contents of these structural units lead to coatings which show these desired properties to only a reduced degree.
In a preferred embodiment, a monofunctional alkoxysilane is employed as component d) in amounts of 0.3 to 1.3 wt. %, together with 0.1 to 2.0 wt. % of a diamino-functional alkoxysilane component c), where the number of terminal alkoxysilane groups must be at least 50 wt. % of all the incorporated alkoxysilane groups. Corresponding polyurethane solutions surprisingly also lead to coatings which meet the stated requirements and moreover have both excellent mechanical properties of the film, in particular a high extensibility and elasticity, and at the same time very high melting or softening temperatures, which is very advantageous for many uses, e.g. in coating of textiles.
With higher contents of lateral alkoxysilane structural units, on the other hand, coatings which surprisingly are significantly less elastic and extensible and have a rather unpleasant, cold handle result. Decreases must then also often be made in the adhesion properties.
In another preferred embodiment, a monoamino-functional reaction product of a monoamino-functional alkoxysilane with 0.5 to 1.1, preferably 0.9 to 1.05 equivalents of maleic acid alkyl esters is employed as component d), optionally together with a diamino-functional alkoxysilane.
Polyurethane solutions which comprise as the stopper agent a reaction product, containing aspartic acid ester structural units, of a compound with a primary amino group and at least one alkoxysilane group with a maleic acid dialkyl ester and additionally a diamino-functional compound containing alkoxysilane structures in a minor amount are also very particularly suitable e.g. for the production of high-quality coatings.
Suitable monofunctional blocking agents e) which are optionally to be co-used in the preparation of the polyurethane solutions according to the invention can be e.g.: butanone oxime, cyclohexanone oxime, acetone oxime, malonic ester, triazole, dimethylpyrazole, monofunctional amines, such as e.g. dibutylamine and diisopropylamine, and monofunctional alcohols, such as e.g. ethanol. If components e) are employed, this preferably takes place such that component e) is added first, and thereafter component d). This ensures that the polyurethane solutions according to the invention no longer comprise unreacted components e).
The amount of stopper reagents d) containing alkoxysilane groups is at least 50, preferably 75, especially preferably at least 95 wt. %, based on the total amount of stopper agents d) and e).
The polyurethane solutions according to the invention with alkoxysilane groups show a storage stability which is appropriate in practice at room temperature up to 75xc2x0 C. After application, drying takes place at room temperature to 200xc2x0 C., preferably at 60 to 160xc2x0 C.
The polyurethane solutions according to the invention with alkoxysilane groups are prepared by a procedure in which an isocyanate-functional polyurethane is first prepared in a one- or two-stage reaction from at least one polyol a) and at least one difunctional polyisocyanate b), optionally co-using a low molecular weight hydroxy-functional component c), and then optionally undergoes a further build up in molecular weight in a further reaction step by reaction with an at least difunctional component c), optionally co-using an at least diamino-functional component d) containing alkoxysilane groups and is reacted in a concluding reaction step with a monoamino-functional component d) containing alkoxysilane groups, optionally co-using a monofunctional component e), to give a high molecular weight polyurethane with alkoxysilane end groups which no longer contains free isocyanate groups, an organic solvent being added either before, during or after the first reaction step in an amount such that the resulting polyurethane solution with alkoxysilane end groups has a solids content of 9 to 65 wt. %.
In one process variant, a one-stage reaction of all the components a), b) and optionally c) can be carried out, usually in the presence of suitable solvents, to give an isocyanate-functional high molecular weight polyurethane, the desired viscosity and therefore the molecular weight necessary to achieve the required properties optionally being achieved by subsequently adding a small amount of polyisocyanate b) and/or low molecular weight difunctional component c), and the chain-stopping reaction then being carried out by addition of a monoamino-functional alkoxysilane. Monoamino-functional alkoxysilanes are preferably employed in amounts of 0.3 to 1.3 wt. % in this process variant.
The reaction of the components as a rule is carried out at room temperature up to 120xc2x0 C., the reaction usually being carried out at a higher temperature, e.g. at 60 to 120xc2x0 C., at the start of the preparation and the reaction being carried out at lower temperatures, e.g. at room temperature to 60xc2x0 C., at the end during the chain lengthening to the chain-stopping reaction.
The reaction of the components can be carried out with addition of conventional catalysts, such as e.g. dibutyltin dilaurate, tin 2-octoate, dibutyltin oxide or diazabicyclononane.
Suitable solvents for the preparation of the polyurethane solutions according to the invention are e.g. dimethylformamide, dimethylacetamide, N-methylpyrrolidone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, toluene, xylene, tertbutanol, isopropanol, ethyl acetate, butyl acetate, methoxypropanol, butylglycol, methoxypropyl acetate and isobutanol. The choice of the nature, amount and time of addition of the solvent or solvent mixtures must be made such that solubility of the end product or of the intermediate stages exists, the viscosities are in a scope which can be managed technically, i.e. usually  less than 200,000 mPas (23xc2x0 C.), and a reaction of the solvents with the raw materials of the polyurethane is very largely ruled out. That is to say e.g. that alcoholic solvents should be used only if only isocyanate-amine reactions or reactions which proceed at a comparable rate take place during the preparation of the polyurethane.
The solids contents of the polyurethane solutions according to the invention are 9 to 65, preferably 20 to 50 wt. %.
The viscosities of the polyurethane solutions according to the invention are 1,000 to 200,000 mPas (23xc2x0 C.), preferably 3,000 to 80,000 mPas (23xc2x0 C.).
The molecular weights of the polyurethane solutions according to the invention can be determined e.g. by gel permeation chromatography. They are between 4,000 and 500,000, preferably between 25,000 and 250,000 g/mol.
Conventional auxiliary substances and additives, such as e.g. stabilizers, light stabilizers, flow auxiliaries, matting agents, heat stabilizers, release agents, antioxidants, UV absorbers, HALS active compounds, defoamers, adhesion promoters, antistatics, preservatives and catalysts, can be added before, during or after the preparation or before or during use of the polyurethane solutions according to the invention.
The polyurethane solutions according to the invention with alkoxysilane structural units are suitable for use in paints, coatings, sealing compositions, printing inks and adhesives. They can be used here by themselves and/or after addition of the conventional auxiliary substances, additives, pigments, fillers, plasticizers, solvents and diluents and/or in combination with other polymers or polymer solutions or oligomers, such as e.g. polyurethane solutions, polyurea solutions, polyurethane-polyurea solutions, co- and homopolymer solutions, chlorinated rubber solutions, nitrocellulose solutions, cellulose acetate/butyrate solutions, polyacrylate solutions, polyether (solutions), polyamide solutions, polyepoxide (solution), polyester (solutions), polyisocyanate (solutions), melamine-aldehyde resin (solutions), urea resin (solutions), polybutadiene solutions or polyolefin solutions.
Suitable fields of use are e.g. coating of textiles, coating of leather, coating of imitation leather, coating and painting of plastics, painting of metals, painting and coating of wood, derived timber products and furniture, coating and painting of all types of mineral substrate and road-marking paints. The polyurethane solutions according to the invention can be employed here e.g. as a primer, intermediate coat, filler, base paint, top paint, clear paint, one-coat paint, microporous coating, adhesive base, top coat, finish, direct coat, intermediate coat or foam coat.
The application can be carried out by all the processes used industrially, such as e.g. pouring, dipping, roller-coating, rolling, brushing, spraying, knife-coating or coagulation.